The long term goals of this research are to define and characterize the molecular mechanisms by which missense mutations in proteins cause neurodegenerative disease. The accumulation of unfolded protein intermediates in various subcellular compartments is thought to underlie pathogenesis for a number of neurodegenerative diseases, including Alzheimers disease. A critical component of this research is the availability of patient data and well-defined animal models in mice so that full use can be made of the extensive tools available for genetic manipulation, such as gene ablation by homologous recombination and the introduction of heterologous transgenes. In Specific Aim number 1 an hypothesis that neurodegeneration stems from the accumulation of misfolded proteins in the endoplasmic reticulum will be tested in greater detail in vitro. These data will be correlated with disease severity in patients as determined by detailed clinical evaluation and in vitro transfection assays. Furthermore, autopsy specimens will be characterized at the levels of RNA, protein and immunocytochemistry to determine if pathogenesis in humans is similar to that in the animal models. In Specific Aim number 2 the pathogenesis of mutant mice, for which signaling pathways normally activated by protein accumulation have been disrupted in knockout mice, will be characterized in detail both molecularly and morphologically to provide a deeper understanding of the involvement of protein misfolding in neurodegenerative disease. In Specific Aim number 3 a number of important genes and proteins recently found to be activated by protein accumulation in the endoplasmic reticulum will be examined at the levels of RNA, protein and immunocytochemistry in mouse models of neurodegenerative disease to determine if protein misfolding activates similar signaling pathways to those identified by other investigators studying different cell types in in vitro systems. Furthermore, the identification of downstream target genes using microarray screens will be sought to identify and characterize the signaling pathways that are activated by unfolded proteins, and ultimately determine if a cell survives or dies. Together, these Aims are expected to identify important pathological processes stemming from protein accumulation and may lead to strategies that ameliorate disease severity. Moreover, the knowledge gained from these studies may be applicable to the amelioration of other neurodegenerative diseases for which protein misfolding is a cause but the genetic or metabolic defects are unknown.